Allocator::allocate() metadata

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Hi.

I was wondering how feasible would it be to add an additional metadata value to the allocate() call of the Allocator trait, something like

meta: Option<&'static str>`

(alternatively the type could be *const () to be more general...)

This would be quite useful for example for a custom memory-leak detecting allocator to keep track of the allocation context - Box::new() could pass the type name here.

Apologies if this has been discussed before, I haven't been keeping up with the talks around custom allocators...

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see Add optional typed variants of allocation and deallocation routines · Issue #89 · rust-lang/wg-allocators · GitHub

In practice, I think the way this is typically solved is by recording the stack trace at the point of allocation. The stack-trace implicitly includes type information (Vec::<MyType>::grow).

Practically, I've found GitHub - koute/bytehound: A memory profiler for Linux. to just work for these kinds of things, highly recommend!

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Yeah, getting it from the backtrace also occurred to me (and tracking allocator needs to save it anyway), but it seemed a bit clunky (different for various containers). But I guess it ends up being a better solution than additions to the alloc api...

bytehound looks cool, thanks

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Using #[track_caller] on your implementation of allocate might work. Not sure how it deals with concrete traits.

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